A Field Study of Soil Water Depletion Patterns in Presence of Growing Soybean Roots: II. Effect of Plant Growth on Soil Water Pressure and Water Loss Patterns
1975
Arya, L. M. | Blake, G. R. | Farrell, D. A.
Soil-water pressure and water-loss patterns in the root zone of soybean (Glycine max L.) genotype P.I. 79.648 were determined from daily observations during irrigation-drying cycles for four growth periods after planting. Tensiometric measurements of soil water pressure were made on a 10-cm square grid from one plant row to an adjacent one spaced 80 cm apart, and between 10- and 70-cm depths. Water contents were inferred from pressure-water content relationships. During the first irrigation-drying cycle, soil-water pressures were marked by strong lateral and vertical gradients. As plants aged from one irrigation-drying cycle to the next, these gradients decreased; soil-water pressures at most depths decreased more slowly with the drying time. The proportional contribution of surface layers to the total water loss from the 10- to 70-cm depth interval decreased as the plants matured while contributions from the lower layers increased. These changing patterns of soil-water pressure and water loss are consistent with the expected shift in root activity.
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